BARLEY Second Edition
CHEMISTRY AND TECHNOLOGY Peter R. Shewry and Steven E. Ullrich, Editors
The Barley Crop: Origin and Taxonomy, Production, and End Uses Steven E. Ullrich Deptment of Crop and Soil Sciences Washington State University Pullman, Washington, U.S.A.
Origin and Taxonomy of Barley The origins of almost all plant species, including the major crop species, and the origins of domestication of crop species are ancient, far predating the human understanding of such things. As such, the determination of the origins of crop species relies on evidence from the archeological record and on scientific investigation using the most up-to-date technologies available at the time, for example, from plant anatomy and morphology, biochemistry, genetics, and agriculture. Therefore, our knowledge and even theories of crop origin and taxonomy are frequently incomplete and subject to periodic change. This is definitely the case for barley (Hordeum vulgare L.), one of the most ancient of crop species, which is currently considered to be among the world’s first crop domesticates. Whereas barley domestication was once thought to have occurred as a single event in the Fertile Crescent of the Middle East at least 10,000 years ago, it is now thought that multiple domestications occurred within the Fertile Crescent (Zeder 2008), with further domestications about 1,500–3,000 km further east in central Asia (Azhaguvel and Komatsuda 2007, Morrell and Clegg 2007). One approach to determining whether a plant species has been domesticated is the presence, in archeological samples, of morphological traits resulting from genetic changes (natural or caused by humans) that favor agricultural production (von Bothmer et al 2003b). In the case of barley, such domestication traits include 1) the presence of a nonbrittle rachis that prevents the spike from shattering and the grain from scattering upon maturity (Fig. 1.1); 2) the change from a two-rowed spike in the wild progenitor barley (H. vulgare subsp. spontaneum) (Fig. 1.2) to the six-rowed spike in H. vulgare subsp. vulgare (Fig. 1.3); and 3) naked or hull-less kernels (Fig. 1.4), which also do not occur in wild barley. Hull-less kernels facilitate the use of barley for human food because of the reduced insoluble fiber in the hull.
Other domestication traits found in barley samples from parts of the world away from the regions of origin include 4) a reduced vernalization requirement and 5) photoperiod insensitivity that facilitates adaptation to different environments and climates (Salamini et al 2002). Barley belongs to the globally and economically very important plant group, the Triticeae, which is a tribe in the grass family Poaceae. This tribe is characterized as having spike inflorescences, a base chromosome number x = 7, and large genomes. In addition to barley, the Triticeae includes the major temperate small-grain cereals: wheat (Triticum spp.); rye (Secale cereale); and triticale (Triticosecale), a human-developed wheat- rye hybrid crop. In addition, the Triticeae includes forage grasses such as the wheatgrasses (Agropyron spp.) and Russian wildrye
Fig. 1.1. Illustrations of a nonbrittle, nonshattering spike (A) and brittle, shattering spikes (B) of wild barley (Hordeum vulgare subsp. spontaneum), which probably represent one of the first selections by humans that began the domestication process of barley. (Courtesy of Brian Steffenson, University of Minnesota; used by permission)
Barley: Chemistry and Technology, 2nd ed.
(Psathyrostachys juncacea), as well as noxious weeds, including a close relative of wheat, jointed goatgrass (Aegilops sp.), as well as quackgrass (Elymus repens), and foxtail barley (H. jubatum). Relatively recent advances in technological tools have increased our knowledge about the evolutionary age, migration patterns, and differentiation of new species in the genus Hordeum, and today the genus is much better understood than ever before. It is estimated that Hordeum is quite ancient, having separated from wheat species about 13 million years ago. The relationships among species within a genus can be relatively close or quite distant. In the case of cultivated barley, most species are rather distant but still related. Biological understanding of the members of the genus Hordeum is very useful in identifying gene sources for improvement of cultivated barley (H. vulgare
subsp. vulgare). The primary gene pool for cultivated barley is the wild subspecies progenitor H. vulgare subsp. spontaneum (Figs. 1.5 and 1.6), which is completely cross-compatible and is increasingly being explored as a source of genes for traits improving cultivated barley, such as pest resistance, nutritional quality, and even malting quality (Fetch et al 2003, Matus et al 2003). Probably the second-best Hordeum source of genes for cultivated barley is the secondary gene pool species H. bulbosum. Initial interest in this species was for doubled haploid production in cultivated barley and wheat, as the H. bulbosum chromosomes are typically eliminated from hybrids (Kasha and Kao 1970, Forster et al 2007). Research has been more recently directed at making viable, stable hybrids between H. vulgare and H. bulbosum in order to transfer desirable genes, especially disease-resistance genes (Pickering and Johnston 2005). Al though hybridization is extremely difficult, there is interest in tertiary gene pool species, such as H. marinum (sea barley) for salt tolerance (Malik et al 2009).
Fig. 1.2. Two-rowed barley spikes of Hordeum vulgare subsp. vulgare, which were inherited directly from wild barley (H. vulgare subsp. spontaneum). (Courtesy of Patrick M. Hayes, Oregon State University; used by permission)
Fig. 1.3. Six-rowed barley spikes of Hordeum vulgare subsp. vulgare, selected from the two-rowed type sometime during the domestication process. (Courtesy of Patrick M. Hayes, Oregon State University; used by permission)
Fig. 1.4. Hulled (A) and hull-less (B) barley kernels of Hordeum vulgare subsp. vulgare. Hull-less kernels were selected sometime during the domestication process. (Courtesy of Byung-Kee Baik, USDA-ARS, Wooster, OH; used by permission)
Barley Crop Hordeum species have migrated from the centers of origin and evolved to other areas around the world, including the Americas. In addition to the species mentioned above, other perennials and annuals are considered to be valuable forage species in natural pastures in central Asia and South America (e.g., H. murinum). H. chilense, from South America, has been used to create a new hybrid species, tritordeum, by crossing with wheat. The contributions from H. chilense include improved baking
quality and resistance to biotic and abiotic stresses (Martin et al 1999). Other species (e.g., H. jubatum) are weedy or have other negative characteristics, such as acting as hosts for pests. This chapter provides only a brief introduction to the origin and taxonomy of barley. Excellent and comprehensive coverage of these subjects can be found in von Bothmer et al (2003a) and von Bothmer and Komatsuda (2011).
Adaptation and Production of Barley
Fig. 1.5. Spikes of wild barley (Hordeum vulgare subsp. spontaneum). (Courtesy of Brian Steffenson, University of Minnesota; used by permission)
Fig. 1.6. Field of wild barley (Hordeum vulgare subsp. spontaneum). (Courtesy of Prof. Brian Steffenson, University of Minnesota; used by permission)
Cultivated barley is adapted to and grown over a wider range of environmental conditions than any other cereal. It is one of the most widely adapted crops in the world and is grown further toward the poles, into deserts, and at higher elevations than any other crop. The author has observed barley growing for grain at higher than 65° N. latitude in Alaska and the Nordic countries of Finland and Norway; toward the margins of the Sahara desert in Algeria, beyond the range of drought-tolerant durum wheat (Triticum durum); and on the Altiplano of Bolivia at 420 m, where the only other cereal planted is oats (Avena sativa) for fodder. Barley is a cool-season crop cultivated in spring and summer at temperate latitudes and in the tropics at high altitudes. It is cultivated in the fall and winter at low and medium altitudes in tropical and subtropical latitudes. Barley is relatively cold-tolerant and is considered the most tolerant to drought, alkali, and salt among small-grain cereal species, but it is not well adapted to wet and acidic soil conditions. Relatively rapid emergence, early maturity, and low water use are the major factors that confer adaptation to drought and high-temperature conditions. Spring types are quite cold-tolerant, but winter types are less winter- hardy than wheat, rye, and triticale. Whereas barley can be and is grown in some of the world’s agricultural margins, it performs best under well-drained fertile loam soils with moderate precipitation (400–800 mm) and temperatures (15–30°C). The role of barley in cropping systems varies throughout the world depending on production environments (e.g., climate and geography) and economic environments (e.g., market supply and demand and the uses for specific types of barley). The adaptation of barley allows it a prominent place in crop rotations in the more marginal production environments of extreme latitude or altitude and low precipitation, but its prominence tends to decrease as production environments become more favorable in terms of temperature regimes and water availability. A good example can be seen in the Pacific Northwest of the United States. Barley is important in the high semidesert of southern Idaho (which has a cool and short growing season and crops are mostly irrigated) in rotation with wheat and potato (Solanum tuberosum). The economic environment is also favorable for malting and brewing cultivars in that there are three malting plants in the area. On the other hand, almost no barley is grown in the low-elevation, semidesert, irrigated Columbia Basin of eastern Washington because the long, warm growing season favors a plethora (more than 50) of higher-value crops such as maize (Zea mays), alfalfa (Medicago sativa), hops (Humulus lupulus), vegetable crops, grapes (Vitis spp.), tree fruits, etc. The same trends can be seen in dryland production environments. Generally, the more crops that are adapted to and can be grown in an area, the lower the prominence of barley in crop rotations. Economics tends to be a
Barley: Chemistry and Technology, 2nd ed.
major factor. Barley usually commands a lower price than other cereals, legumes, and oilseeds because it is primarily used for feed. On the other hand, demand for malting barley can equalize the profitability since malting barley cultivars usually command a significant premium over those of feed. A good example is in central and northern Europe, where the temperate and relatively wet growing conditions tend to be quite favorable for several cool-season crops (such as wheat, oilseeds, and Brassica vegetable and forage crops). However, the demand for malting barley in this area is high, which keeps barley production high. France and Germany tend to be the biggest producers of barley in Europe, and they also rank high globally, as described below. Barley also ranks high in production in cool Canada and semiarid Australia but less so in the United States, which has more favorable growing environments. Maize and soybeans (Glycine max) dominate in the United States, and the highest-ranking barley- producing states all border Canada, from the Pacific Ocean through the Great Plains to the Great Lakes. Barley is grown under a wide range of growing conditions in terms of climate, tillage, fertility, moisture, and crop rotation. Compared with wheat, which is relatively closely related, barley generally requires less water and plant nutrients, primarily because it has a shorter growing season. Earlier maturity also means that it can escape drought, disease, and insect stresses better than wheat under many conditions. A recent summary of barley agronomic practices can be found in Ullrich (2011), which includes a chapter covering the major barley-producing areas of the world. Barley is a major world crop, ranking fourth among cereals and fifth overall in millions of tonnes produced per year. The global production of barley, averaged over the first 11 years of the twenty-first century, was estimated to average 141 million tonnes per year, behind maize (715), rice (Oryza sativa) (628), wheat (618), and soybean (207), as shown in Table 1.1. Barley is also ranked fifth based on estimated land area harvested per year in millions of hectares (ha), after wheat (217), rice (153), maize (148), soybean (89), and barley (55). Production estimates are based on data from the Food and Agriculture Organization (FAO) of the United Nations (FAO 2012b). The trends of the top five produced crops over the past 50 years from 1961 through 2010 indicate some major dynamics and shifts in rank (Table
TABLE 1.1 Global Production Average Estimatesa of the Top Eight Crops for 11 Years (2000–2010)b Crop
Maize Rice (paddy) Wheat Soybean Barley Sugarcane (dw) Potato (dw) Sorghum a Expressed b Source:
Production (million t)
Area Harvested (million ha)
Grain/Crop Yield (t/ha)
715 628 618 207 141 99 61 59
148 153 217 89 55 22 19 43
4.8 4.2 2.8 2.3 2.6 4.7 3.2 1.4
“as is,” except dry weight (dw) for sugarcane and potato. FAO (2012b).
1.2). Barley production peaked in 1990 at 178 million tonnes, then steadily declined to 134 million tonnes in 2011, the final year of FAO data available at this writing. Barley production ranked fourth in the world from 1961 until 1998, when soybean production eclipsed that of barley (160 vs. 138 million tonnes). While barley production rose and fell over this 50- year period, the other four crops steadily rose in production, most notably maize and soybean. The production of wheat was highest among these five crops until 2000, when rice production eclipsed wheat, and maize eclipsed them both. The rank of the top five crops has not changed so far in the twenty-first century (Table 1.1). The percentage of 2011 production over that of 1961 is quite remarkable for the top five crops: soybean, 967%; maize, 431%; rice, 335%; wheat, 317%; and barley, 186%. Soybean production largely accelerated as a result of increased oil and protein demand and maize production because of the phenomenal performance of hybrids. Both of these crops have received large increases in breeding and genetic research funding from the private and public sectors. The improvement and proliferation of rice hybrids have contributed to rice production increases. The rise in population in South and East Asia, resulting in a rise in demand, is also a factor in rice production increases. Increases in soybean acreage in South America, especially in Brazil and Argentina, and in the U.S. Midwest have been drivers. Increased demand for biofuels has affected maize and soybean acreages. Note that these are somewhat simplified explanations of considerably complex situations. Barley production is widely distributed around the world. The FAO barley database includes production estimates from 98 countries. Table 1.3 shows five-year (2007–2011) average barley production according to continents and regions within continents. The greatest production by far is in Europe, including the Russian Federation, at 88 million tonnes or 64% of the world production, of which approximately two thirds is from the European Union (EU) of 27 countries. Asia ranks second at 20 million tonnes or 14% of the world production, with about half from western Asia; followed by North America (mainly Canada and the United States) at 14 million tonnes (11%); Australia and New Zealand at 8 million tonnes (5%); Africa at 6 million tonnes (4%), with two thirds of that from North Africa; and finally South America at 3 million tonnes (2%). The Russian Federation heads the list of the top 20 barley-producing countries in the world, based on eight-year averages (2003–2010) of total production amount (16.6 million tonnes, or approximately 12% of the 142 million tonnes world total) and area of production (8.4%, or TABLE 1.2 Global Trends for Production (million t) of the Top Five Crops in the World over 50 Years (1961–2010) a Year
1961 1971 1981 1991 2001 2011
2,222 348 450 547 590 704
216 318 410 519 600 723
205 314 447 494 616 883
72 132 150 170 144 134
27 46 89 103 178 261
Barley Crop approximately 15% of the 55 million hectares world total) (Table 1.4). The other top five countries include Germany (11.7 million tonnes), Canada (11.1), France (10.7), and Ukraine and Spain (9.3 each). Sweden, at number 20, produced 1.6 million tonnes. Nine of the top 20 countries are EU members, with the highest national average yields being from the northern EU countries France, Germany, United Kingdom, and Denmark at 7.1, 6.7, 6.7, and 5.8 t/ha, respectively. TABLE 1.3 World Distribution of Barley Production Based on Estimates, Five-Year Averages (2007–2011)a Region
World Europe European Union Asia West Asia South Asia East Asia Central Asia North America Australia/New Zealand Africa North Africa East Africa South America a Source:
Number of Countries
Production (million t)
102 37 27 31 16 7 5 5 2 2 16 6 6 8
140 88 58 20 9 5 3 3 14 8 6 4 2 3
TABLE 1.4 Barley Production Estimates by Country, Eight-Year Averages (2003–2010)a Rank
1 2 3 4 5 5 7 8 9 10 11 12 13 14 15 16 17 17 17 20
World Russian Federation Germany b Canada Franceb Ukraine Spainb Turkey Australia United Kingdomb U.S.A. Polandb Denmark b China Iran Morocco Czech Republicb Kazakhstan Finlandb Belarus Swedenb
Production (million t)
Harvested (million ha)
142 16.6 11.7 11.1 10.7 9.3 9.3 7.9 7.4 5.7 5.0 3.7 3.4 3.1 2.9 2.1 2.0 1.9 1.9 1.9 1.6
55 8.4 2.0 3.5 1.7 4.4 3.2 3.4 4.5 1.0 1.4 1.1 0.7 0.8 1.5 0.5 … … … … …
2.6 2.2 6.7 3.6 7.1 2.5 3.1 2.8 2.0 6.7 4.0 3.6 5.8 4.3 2.1 4.2 … … … … …
FAO (2012b). Union member country.
Uses of Barley Barley has had many and diverse uses, which have evolved, waxed, and waned over the millennia from hunting and gathering times, through the development of agriculture, and up to today. Carl Nilsson Linnæus must have been thinking of barley use when he gave the scientific or Latin name to barley, Hordeum vulgare. Hordeum derives from hordearii, the Latin name for gladiators, and translates to “barley men.” This is because barley was a primary component of the training diet of gladiators, which gave them strength, stamina, and subcutaneous fat (Percival 1921, Curry 2008). A layer of fat protected the gladiators from relatively superficial wounds, but the bleeding from these wounds excited the crowds in the arena (Curry 2008). When people think about barley use, animal feed, malt, and/or beer or whiskey usually come to mind. However, as the term hordearii implies, barley has been and still is used for food. Archaeological evidence also suggests that barley was first used primarily for food (Harlan 1979, Grando and Macpherson 2005). The usefulness of fermentation was also discovered early (Hornsey 2003). As free-threshing “naked” grains, such as wheat, evolved with agriculture and became increasingly popular, the predominantly hulled barley for human food was relegated to the poor, and its use for animal feed became increasingly prominent (Grando and Macpherson 2005, Newman and Newman 2008). Nevertheless, barley remains an important component of the diets of several cultures across North Africa, the Horn of Africa, the Middle East, and Himalayan nations to the present day (Grando and Macpherson 2005). Globally, barley is currently primarily used for feed, at approximately 60–70% of the total production. Malt for brewing, distilling, and food makes up most of the rest at 30–40%, while seed use is about 5%, and direct food use is only 2–4% (Newman and Newman 2008). Barley for feed dominates in areas where small grains dominate cereal production, notably areas that are unable to produce maize, such as northern North America and Europe, high and/or dry areas of South America (in the Andes), Asia (the Middle East, central Asia, and the Himalayan regions), and Africa (North Africa and the Horn). The composition of barley makes it particularly suitable as a high-energy food and feed. In common with other cereal grains, the relatively high energy content of barley is derived from starch. The composition data presented here are based on several studies and compilations (Åman et al 1985, Åman and Newman 1986, Ullrich 2002, Newman and Newman 2008). Note that these data represent average estimates for barley in order to give a broad overview, but the contents of components vary considerably among samples due to genetic and environmental impacts. The ranges quoted do not necessarily include data for particular extreme genotypes or mutants. For example, most commercial barley cultivars are hulled, but hull-less types exist and are important in some feed and food applications. Hull-less types (Fig. 1.4) tend to have elevated levels of most inner-kernel components because the fibrous hull is missing. The waxy, or high-amylopectin and low-amylose, trait in barley tends to be associated with higher levels of soluble fiber. Extreme differences can also exist in protein levels due to specific genetics and/or extreme levels of moisture or nitrogen in the environments. The
Barley: Chemistry and Technology, 2nd ed.
concentration of starch in whole-grain barley typically ranges from 50 to 65% of the dry weight. Barley also has a moderate protein level of 10–16%, which is higher than that in many other cereals (e.g., maize and rice have <10%). Barley has a fairly balanced composition of essential amino acids, except for lysine, which tends to be limiting for nonruminants. It also has relatively high contents of total fiber due to the hull (13–22%) and of soluble fiber (5–7%) due primarily to high levels of β-glucan (3–6%). β-Glucan can cause digestive tract disruptions in poultry but can have significant advantages for humans, as it has been implicated in lowering blood lipids and cholesterol in humans and reducing the glycemic index of foods (summarized by TABLE 1.5 World Trade Estimates of Barley and Barley Products for 2003 and 2009a 2003 Commodity
Barley grain Quantity (million t) Value (billion $US) Malt Quantity (million t) Value (billion $US) Beer Quantity (million t) Value (billion $US) Malt extract Quantity (thousand t) Value (million $US) Pearled barley Quantity (thousand t) Value (million $US) Barley flour/grits Quantity (thousand t) Value (million $US) a Source:
Behall and Hallfrisch 2006, Pins and Kaur 2006, Lazaridou and Biliaderis 2007). Similar effects on serum cholesterol and lipids were reported earlier in chickens and eggs (Bengtsson et al 1990), rats (Kalra and Jood 2000, Li et al 2003), and pigs (Bird et al 2004). Barley has relatively low levels of lipids (2–3%) but is known to have relatively high levels of vitamin E and other tocols (Moreau et al 2007), which have antioxidant activity. It has the highest levels of tocols in the grain compared with the other major cereals, according to Kerckhoffs et al (2002). Detailed reviews of barley grain composition can be found in Gubatz and Shewry (2011) and in Chapters 4 (carbohydrates), 6 (protein), and 7 (lipids) of this book. The trade of barley essentially reflects barley use. The FAO collects data on import and export activity for various forms of barley, malt, and beer (FAO 2012a). A general picture of the export and import of barley and barley products is given in Table 1.5, which includes data for the quantity and value of products for 2003 and 2009. In general, the quantity and value of exports and imports increased in 2009 as compared to 2003. However, some drastic differences can be seen between the two years for some products, i.e., the value of barley and barley products exported and imported generally doubled between 2003 and 2009, whereas the differences were not as drastic for quantities traded. Table 1.6 presents a similar snapshot of trade, indicating the leading exporting and importing countries. It is not surprising that the leading exporters (Table 1.6) were also generally the leading producers (Table 1.4). With the exception of Mexico and the Netherlands, which are not among the top 20 barley producers in the world (Table 1.4), the leading barley producers were the leading beer exporters in the world in 2000 and 2009. On the other hand, the leading importers did not necessarily follow the same trends, i.e., low producers were not always the leading importers. The top 10 barley beer producers, globally, for the three years 2006, 2008, and 2010 are listed in Table 1.7. The global production and top annual producers of sorghum, maize, and millet beers for 2006 are listed for comparison. Whereas the produc-
TABLE 1.6 Two-Year Snapshot of Leading Barley-, Malt-, and Beer-Exporting and Importing Countries, Showing Quantity Estimates (million t)a 2000 Barley
World Germany France Australia Canada U.K.
24 6.2 4.8 3.0 1.8 1.6
World France Belgium Germany Canada Australia
6 1.1 0.60 0.55 0.50 0.47
World Mexico Netherlands Germany Belgium Canada
6 1.05 0.80 0.79 0.43 0.39
Exporters World Ukraine France Russian Fed. Australia Canada
26 5.5 4.7 3.5 3.2 1.6
World Belgium France Canada Australia Argentina
6 0.97 0.95 0.63 0.55 0.48
World Netherlands Mexico Germany Belgium U.K.
11 1.7 1.6 1.4 1.0 0.6
World Saudi Arabia China Japan Belgium Iran
22 5.4 2.1 1.7 1.2 1.0
World Japan Brazil Russian Fed. Germany Venezuela
5 0.74 0.64 0.56 0.31 0.26
World U.S.A. U.K. Italy France Germany
6 2.35 0.44 0.42 0.37 0.32
Importers World Saudi Arabia China Belgium Netherlands Syria
25 6.0 1.8 1.6 1.6 1.5
World Brazil Belgium Japan Mexico U.S.A.
7 0.83 0.56 0.50 0.35 0.33
World U.S.A. France Italy Germany Canada
11 3.00 0.59 0.58 0.57 0.35
TABLE 1.7 Leading Beer-Producing Countries Based on Estimates of Quantity Produced (million t), 2006–2010a Barley beer World China U.S.A. Russian Fed. Germany Brazil Mexico United Kingdom Japan Spain Poland Sorghum beer World Tanzania Uganda Nigeria Burkina Faso Congo South Africa Cameroon Ghana Maize beer World South Africa Uganda Canada Congo Zambia Millet beer World Uganda Tanzania Ethiopia a Source:
165 35.9 23.2 10.0 9.9 9.4 7.8 5.4 3.8 3.4 3.3
176 41.4 23.2 11.4 9.4 10.6 8.2 5.0 3.4 3.3 3.6
169 36.9 22.8 10.3 8.9 11.4 8.0 4.5 3.5 3.3 3.4
6.9 1.92 0.82 0.79 0.64 0.59 0.56 0.42 0.34
… … … … … … … … …
… … … … … … … … …
2.5 0.90 0.62 0.52 0.14 0.14
… … … … … …
… … … … … …
1.5 0.34 0.33 0.21
… … … …
… … … …
tion of these beers is relatively small compared to that of barley beer, it is important to the producing countries. All countries listed for these other beers are from Africa, with the exception of Canada for maize beer. The top 10 barley beer producers can be considered in three categories. China and the United States have been consistently the top two producers at roughly 20+ to 35+ million tonnes per annum, followed by the Russian Federation, Germany, Brazil, and Mexico (third to sixth ranking, respectively) at about 8–10 million tonnes, with the United Kingdom, Japan, Spain, and Poland at 3+ to 5+ million tonnes. Many factors, such as production levels, which are affected by climatic and economic conditions as well as political and population situations, may affect the amount and variation of barley and barley products that are exported and imported. Feed Uses
Barley is prepared in various ways for feed, depending upon the objective (growth, maintenance, or finishing) and the ani-
Fig. 1.7. Spikes of hooded, six-rowed barley, typical of forage cultivars. (Courtesy of Patrick M. Hayes, Oregon State University; used by permission)
mal species. Barley grain may be fed whole and raw, dry-rolled, steam-rolled, or ground. It is fed primarily to swine (pigs) and ruminants (cattle, sheep, and goats) but is also used for poultry, dogs, and farmed fish (Bregitzer et al 2007, Blake et al 2011). As noted above, poultry are particularly sensitive to soluble fiber components in the grain, so β-glucanase is often included in the ration (Kellems and Church 2002). Barley plants are also used as forage, including hay, haylage (between hay and silage in moisture content), silage, and greenchop (high-moisture feed, used directly from the field), as well as for pasturage and straw (Kellems and Church 2002). Barley for forage often uses cultivars that are awnless or hooded (Fig. 1.7) to avoid the barbed awns that are present on most barley cultivars. This is because the awns, depending on the stage of maturity, can cause injury to the mouths of livestock. Forage barley is typically fed to ruminants and, to a lesser extent, swine. Comprehensive reviews of feed uses and processing of barley can be found in Kellems and Church (2002), Ullrich (2002), Blake et al (2011), and in Chapters 9 and 10 of this book. Malting, Brewing, and Distilling Uses
The use of fermentation for making various types of beverages is ancient, going back to at least the dawn of agriculture and probably associated with permanent settlements (Harlan 1992, Hornsey 2003, McGovern 2003). Of course, the technology of malting, brewing, and distilling of barley has advanced through the millennia to the high level that exists today. At the same time, tradition plays a key role in the execution of these processes, in no small measure because malting and fermentation are natural biological processes. Whereas raw barley grain can contribute to the making of some distilled fermented beverages (e.g., Japanese shochu and Korean soju), malting is a critical first step in the making of beer and distilled liquors such as Scotch whiskey and Irish whiskey. Malt also has uses beyond being a raw material for beer and whiskey. Malt extract and flour are used in confections and in many wheat-based baked products
Barley: Chemistry and Technology, 2nd ed.
to add flavor and stability, while brewers’ spent grain is used for feed and has potential use for food (Newman and Newman 2008). Comprehensive current reviews of malting, brewing, and distilling can be found in Chapter 8 of this book and in Schwarz and Li (2011). Food Uses
As noted above, a relatively small proportion of the barley produced globally (2–4%) is used directly for food. However, some cultures depend heavily on barley for food. Furthermore, the dynamics of barley food-product development and use is changing in many parts of the world where barley has never been used extensively or has not been used extensively for many years. This renewed interest in barley-based foods is partly the result of the increased emphasis on including a variety of whole grains in the diet as a functional-food approach to preventing or alleviating various diseases, including heart disease, hypertension, diabetes, and obesity. Another significant aspect is the scientific evidence that barley’s soluble fiber (mainly β-glucan) can reduce blood cholesterol and the glycemic index of foods, which can impact both heart disease and type II diabetes. These findings were the impetus for the U.S. Food and Drug Administration to issue a health benefit endorsement for barley foods in 2006 (U.S. FDA 2006). The increasing use of barley in the United States in grain products such as multigrain breads, breakfast cereals, and energy bars has been clearly noticeable in the last decade. The methods for processing barley for food products include pearling, grinding or roller milling into flour (whole-grain or sifted), steel cutting, rolling or flaking, extruding, and malting (Newman and Newman 2008). Pearled barley can be used in several food preparations (such as soups, pilafs, and casseroles), while flour from the whole grain or pearled grain can be included with wheat or rye flour in yeast breads or used alone in flat breads, pastas and Asian noodles, pastries, etc. Steel-cut, flaked, or extruded barley can be used in breakfast cereals and snack foods. Malt flour is used in an array of wheat-baked products and can be used for confectionary products. In principle, barley can be used for almost any product currently made from wheat, rice, or maize. In fact, the potential is far from being realized commercially in most industrialized nations. In certain areas of the world today, barley is an important food ingredient, regularly used in the human diet. These areas tend to be where other cereals do not grow well, such as arid and high-elevation regions of countries in North Africa (Morocco, Algeria, Tunisia, Libya, and Egypt), in the highlands of the Horn of Africa (Ethiopia and Eritrea), in the higher dry lands of the Near East (Iran and Yemen), in the highlands of Central Asia (from Tibet and Nepal to the republics to the west), and in the Andean countries of South America (particularly Ecuador, Peru, and Bolivia). Communities in several East European countries have also retained traditional barley foods, notably in Estonia, Latvia, Lithuania, and Moldova (Grando and Macpherson 2005). The traditional use of barley foods in Nordic and Far Eastern countries has decreased relatively recently, but these foods are still popular in certain situations or areas. Relatively recent comprehensive reviews of barley food processing and food use include Grando and Macpherson (2005),
Baik and Ullrich (2008), Newman and Newman (2008), Baik et al (2011), as well as Chapters 9 and 10 of this book. Other Uses of Barley
Barley also has other uses, either current or potential. Some of these are industrial uses of barley starch for paper and fabric manufacturing, paper pulp, construction-grade fiber board, biofuels, and industrial chemicals such as ethanol and methanol (Bjørn Petersen and Munck 1993, Munck 2004). The biofuels industry is booming in some areas of the world, with ethanol production from barley and other grains, and the potential exists for the production of ethanol from cellulose in barley straw (Kim et al 2008, Mullen et al 2010, Nghiem et al 2011). See Chapter 11 of this book for a detailed summary of barley use for biofuels. A myriad of products for various food, feed, and industrial uses could be derived from barley grain and straw, comparable to those that have been produced for decades by dry and wet milling of maize grain (Griffey et al 2010). The germination of barley grain and the fermentation of barley grain and straw could also generate many products for various industries (Munck 2004). References
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Published on Mar 5, 2014
Barley: Chemistry and Technology, Second Edition is an important tool for any cereal chemist, food scientist, or crop scientist who needs to...